Imagine you are enjoying your golden years, driving to your daily appointment for some painless brain zapping that is helping to stave off memory loss. That's the hope of a new study, in which people who learned associations (such as a random word and an image) after transcranial magnetic stimulation (TMS) were better able to learn more pairings days and weeks later—with no further stimulation needed. TMS uses a magnetic coil placed on the head to increase electrical signaling a few centimeters into the brain. Past studies have found that TMS can boost cognition and memory during stimulation, but this is the first to show that such gains can last even after the TMS regimen is completed.
In the new study, which was published in Science, neuroscientists first used brain imaging to identify the associative memory network of 16 young, healthy participants. This network, based around the hippocampus, glues together things such as sights, places, sounds and time to form a memory, explains neuroscientist Joel Voss of Northwestern University, a senior author of the paper.
Next, the researchers applied TMS behind the left ear of each participant for 20 minutes for five consecutive days to stimulate this memory network.
To see if participants' associative memory improved, one day after the stimulation regimen finished they were tested for their ability to learn random words paired with faces. Subjects who had had TMS performed 33 percent better, compared with those who received placebo treatments, such as sham stimulation.
“Twenty-four hours may not sound like a long time, but in fact that's quite long in terms of affecting the brain,” Voss says. His team followed up with the participants about 15 days later and found the benefit remained, according to another paper in press at Hippocampus. The team also imaged the subjects' brains one and 15 days after stimulation, finding increases in neural connectivity in their associative memory network.
Voss now plans to test whether this method works on individuals who have disorders in which the memory association network is weak, such as Alzheimer's disease, traumatic brain injury and schizophrenia.